[ARC5] [BoatAnchors] Sharpening the RU Receiver with Regeneration

[Brian Clarke]

Hello Dave,

Great looking components. However, I would suggest a few layout mods:
1. Shift the antenna changeover box to the very top of your control stack so 
neither you nor any other 'investigator' can get across the RF at PTT time
2. Put the remote tuning control at the bottom of the control stack so it's 
closest to your 'operating' hand
3. Remove the right-angle drives in the tuning cable set-up - they will add 
friction and require lubrication, compared with a straight tuning cable.

Otherwise, well done!

BTW, your 121 connectors went to your Nevada, Texas address yesterday by 
Airmail.

73 de Brian, VK2GCE.

On Sunday, April 14, 2013 4:02 AM, you shared with us:


> With the very kind help of many of our members, I've gotten the GF-10 / 
> RU-15 Naval Reserve Command Set up and making contacts.
> Still need to dress cables, clean and touch-up some spots
> and mount the "Test" meter, but it's getting close:
>
> http://home.netcom.com/~arc5/GFRU.JPG
>
> The RU is a TRF receiver and was intentionally designed to
> be broad.   To "tighten it up" for use on the Amateur bands
> one can introduce regeneration between the TRF stages.
> I've been "noodling" how to do this in a simple, non-destructive way. 
> The answer was indeed simple:
> Strip a quarter-inch of stiff hook-up and tuck that end
> under the grid cap of the second tube from the front.
> Run the wire out the top.  Bend the other end back on
> itself to make about a three-inch "loop" and poke it through the side vent 
> hole nearest the grid cap of the fourth tube.  The idea is to use friction 
> between the sides of the vent hole and the loop to keep the loop
> in place.  Tune to the freq you want, then *carefully*
> move the loop in and out until the regeneration is just right.
> It is very touchy and will require effort, but you will be rewarded with 
> weak signals coming up out of the noise
> and sharp tuning.  If it motorboats, pull the loop back a bit.
> In fact, you can get the bandpass TOO sharp and distort AM audio.
> The audio output level will also have an effect on regeneration.
>
> Here is a short .WMA video file showing what can be done if you work at 
> this.  The two QSOs from this morning
> were at 3880 and 3890 KCs.  I did not get the bandpass as tight as I could 
> have.   You can see the white feedback wire in the background.
> With no regeneration, you would hear both QSOs at some level.  The file is 
> a just under 4 MB:
>
> http://home.netcom.com/~arc5/RURegen.wmv
>
> Use "MANUAL" mode when adjusting regeneration.
> As with any regen receiver- if you move far in frequency,
> you must re-adjust the regeneration.  However, this is offset, at least 
> for me, by the fact that AM activity here
> is limited to a few established frequencies.  I don't need to change 
> things around often.  I'm not trying to work
> the Itchy Armpit, Idaho QSO Party afterall.
> I'm thinking of how to use the vent hole as a mounting point for a
> "hank-n-whack free," screw-adjustable feedback plate which could be moved 
> back and forth with a knob adjustment.  This is similar to the idea used 
> in the U.K. TR9D, where a phenolic cylinder with a long screw adjustment 
> creates a fractional-picoFarad capacitor used for smooth control of 
> regeneration.
>
> More on the project later.
>
> 73 DE Dave AB5S